Process for manufacturing paper



Patented 11, 11938 UNITED STATES I PATENT OFFlCEI PROCESS FOR, MANUFACTURING PAPER Jolian Oltmans, Groningen, Netherlands a No Drawing. Application April 22, 1936,-Serlal No. 75,887. In Great Britain and France 0ctober 8, 1931 7 Claims. (01. 92-21) facture of the paper; all as more fully herein- Gil after set forth and claimed. It is an object of the invention to secure superior paper with the aid of cold swelling starch.

The manufacture. of paper with cold swelling starch presents numerous advantages .over former processes in which the pulp has been sized with the aid of materials such as potato starch, resinous soap, etc.

In comparison with the process of'sizing with potato starch, the use of a cold swelling starch has the advantage of avoiding the heat treatment necessary when a substance such as potato starch is used which is then liable to coagulate.

The paper obtained by the process according to the invention has special and unexpected properties as compared with the paper manufactured by known processes.

Thus for example, in comparison with paper sized withordinary potato starch, the paper formed by the new process has a much greater resilience, especially as to tearing, folding and perforation than paper manufactured from a similar pulp but sized in the ordinary manner. The paper manufactured according'to the present invention also has under the same conditions a far greater impermeability. The amount of increase of resistance of the paper to tearing, -folding-and perforation and the amount of increase of' its impermeability will depend on the quantity of cold swelling starch present in the paper manufactured.

Because of the special properties secured when a cold swelling starch is used, the paper itself constitutes a new product.

The incorporation in the paper of a cold swelling starch may be made in any desired manner. Thus according to a first method of carrying out the invention, the cold swelling starch may be added in the dry state to the primary materials at the time of the preparation of the pulp and at any stage of this preparation. For example, it may be introduced in a dry state:

(a) In the dlsintegrators or grinding machines during the comminution of the primary materials such as cellulose, wood pulp or old papers;

(b) .In the rag engine, either in place of the sizing material ordinarily used, or in mixture with the latter. pulp is prepared in the ordinary manner until it is passed into the rag engine.

According to a second method of carrying out the invention, a solution is prepared in water of In the latter case the papera cold swelling starch and this solution is incorporated either in the primary materials at the preparation'of the pulp, at the comminution of their treatment or at any phase of the latter, or

in the water used for preparing the pulp.- In

either case, with this pulp, the manufacture of the paper. is continued in the ordinary manner. According to a third method of carrying out the invention the cold swelling starch is incorporated as a solution in the paper at any other stage of its manufacture. For example, this solution can be incorporated in the paper sheet itself. The solution could be spread on the sheet by the. couching cylinders or at the commencement or at any other part of the drying process or by the immersion or dipping of ,the sheet in a bath of a cold swelling starch or by any other means.

By Way of example and without limiting the scope of the present invention, it may be men'- tioned that papers having the new valuable properties can be obtained by adding to the paper pulp in the rag engine, a quantity of cold swelling starch comprising between 0% and 5% of the weight of the paper obtained. A higher percentage may be utilized for special papers.

I have found that by using cold swelling starch in making paper much better results can be ob-. tained than by the use of starch in other forms. Unlike raw starch, it suspends well in the beater and does not undergo cooking changes when the paper is heated in drying. Its great dispersability in the beater enables the use of very small proportions in even distribution; a type of distribution which is extremely difficult to obtain with any other form of starch or starch preparation. cellulose fibers and is not so easily washed-away with water; there is considerably less loss in the white water. Cold swelling starch has an 150- The starch is retained far better by the electric point causing it to be particularly well retained by the fibers when the pH is changed by the addition of aluminum sulfate (alum) in ordinary ways of making paper. Paper made in the new'way, it is found. has m- 2 I better mechanical properties with respect to folding, Mullen and breaking strength. In addition,

the use of cold swelling starch also has a favor- Results in first paper mill I Beating Beating Beafl'n Beating time 7 time 6% time time 7 hours hours hm titty it W o o 0 322.23 corncold lad starch swelling swelling arc starch 32% 32 32% 32+ 006 0. 0065 0. 0065 0. 0065 30 35 38 39 so 78 84 se Tear (cross direction) 73 70 78 79 Fold Emachine direction)- 74 77 100 112 Fold cross direction)..- 26 92 94 Density 23B 242" 3'16" 3' 25' Ink 7'l" 652" 8-27 8-52' Our]. 47" 40" 55- 52" Stiffness 29-30" 8'-9 l820 1013" Opacity--- 4'5" 23" Colour 1 1 l 1 Results m second paper mill 6% beater 1% cold starch swelling 1% resin starch alum to pH resin Weight 18% Caliper D. 004 0. 004 Mullen test 20 28 Tear (machine direction) 54 67 Tear (cross direction) 38 50 Fold (machine directio 46 64 21 56 1'-22" l52" 2! 46II 3I 3fi!l 32/! 35!! 4650 4244" 8I gl 5I 6II Good Good The figures in each of the above two reports are averages of .60 tests, whileevery series consists of 6 beaters of 1,200 lbs; each. I

While in general papers made with the aid of ordinary starches are liable to picking when being printed i. e. stick to the blocks under the influence of the wet printing ink, which inconvenience appears. especially with papers made Without starches, papers made with a cold swelling starch are entirely free from picking. This advantage of papers made with a cold swelling starch may be attributed to the irreversibility of the cold swelling starch colloid. In other words in contrast with a dried ordinary starch film which and better.

It is also a well-known fact that with chang ing degrees of humidity of the air it is very diflicult to make a paper which has all the requirementsnecessary for correct. register in multicolor printing. Most papers and especially the papers treated with ordinary starch shrink orexpand 'under the influence of the first ink which necessarily causes a lack of register oi the paper.

Due to the firmness of the cold swelling starch film and its irreversibility the register of paper made with a cold swelling starch or the surface of which has been sized with a cold swelling starch improves considerably.

A further improvement caused by the use of a'cold swelling starch is the following. The majority of the disadvantages connected \.ith fastrunning paper making machines are located between the wet-calendar and the first drying cylinder. At this stage the paper is often too weak to withstand the speed of the machine. strength of the wet paperis influenced very favorably by the addition of cold swelling starch and due to this and also to the quicker-drying the speed of paper machines may be considerably increased. This increase in speed'of paper machines has in some instances amounted to 20%.

Moreover, in cold swelling starch the amylose and amylopectin are no longer present separately, one alongside the other, but they arein fact so consolidated as to form a. homogeneous mass which acts like and has the properties of pure amylopectin. This will cause a paste of a cold swelling starch as pointed out above, to have a more pronounced iso-electrical point and furthermore, such a paste when allowed to stand, will maintain its original gum-like properties for a far longer time than ordinary raw starch and especially far longer than thin boiling, chemically treated, soluble, attrition or converted waste water must be neutralized before use to about pH 7. After-adding and dissolving the cold swelling starch the pH value is reduced to about pH 5 or pH 4.5, preferably by adding alum. This is necessary in order to obtain with this product the'greatest possible effect and also in order to fix the cold swelling starch in the-paper pulp.

The incorporation of the cold swelling starch into the paper pulp is preferably effected at an early stage in the beater, at which stage the water does not as yet show an acid reaction, but is neutralor onlyslightly alkaline and after the I cold swelling starch is dissolved, then the pH is lowered to about 4.5 by the addition of alum.

It has also been found that the properties 01 the cold swelling starch may be improved by adding before, during or after its manufacture, various chemicalswhich have an influence on the properties of the cold swelling starch, e. g. aluminium compounds such as alum, aluminium sulphate or alkali aluminates, feebly alkaline salts of sodium and potassium, such as borax or sodium phosphates, albuminous substances, etc. These additions do not cause a decomposition or hydrolysis ,of the starch because in such case the same results would only be obtained as are secured with a thin boiling, chemically treated,

soluble, attrition or converted starch. In such case, the starch would dissolve and owing to the high dispersity oithe solution it would not be satisfactorily retained bythe fibers.

The percentage of starch retained in the paper when a cold swelling starch is used is far above the percentage retained when ordinary starches are used. When ordinary starches are used the The.

percentage of starch retained in the paper is on an average '40 to 45% and the remainder flows away with the back water. However, a cold swelling starchis retained by the paper pulp to the extent of at least 85%. Because of this not only a larger yield is obtained, but another consequence thereof is the, reuse of the back water has been simplified since the back water is much cleaner than in former processes.

According to the invention starch products are used in a new and special form in which they have a quite distinct and better influence upon the paper than the ordinary starch products. heretofore used. Asis well known, the addition of ordinary starch to the pulp in the manufacture of paper has a favorable influence upon the properties of the paper. Such starch is mostly used in the form of ordinary starch which is boiled with water or 'heated until-it is swollen. Furthermore, the starch may be used inthe form of a thin boiling starch, or a chemically treated starch, or a soluble starch, oran attrition starch, or a converted starch, etc.

When using ordinary non-modified starch or raw starch, this is customarily admixed with water and heater or boiled so that the starch granules will'swell and form a thick paste. Soluble starch, converted starch, chemically treated starch or thin boiling starch are insofar different from the above raw starch that when mixed with water and heated they producepastes which have a lower viscosity and the solutions have a higher transparency. The dispersity of these starch solutions is higher than that of the paste obtained by heating raw starch which cannot be considered a solution, properly speaking.

A thin boiling starch, a chemically treated starch, a soluble starch, an attrition starch or a converted starch are insoluble in cold water but such starches are soluble in hot water. By the term "converted starch above is included such starch products as are obtained by stirring the starch with water and strong alkalies such as caustic soda or sodium silicate. By this procedure the starches are converted into alkali starches which can form solutions which also have a higher dispersity than the pastes obtained by boiling raw starches. Solutions so obtained correspond with those of the chemically treated, thin boiling or soluble starches with the prising inasmuch as other forms'of starch have for a long time been used in the manufacture of paper.

By the term cold swelling starches it must be understood that such starch products are meant which when mixed with a quantity of cold waterof many times their weight, say 10 to 15 times the weight of the starch, will form a thick cohering mass and with greater amounts of water will form a good and tolerablyperma- 'nent dispersion.

.Whenever raw starch is mixed with cold water the raw starch will settle to the bottom and form .a layer. This is also the case with the chemically treated, thin boiling, soluble, attrition and converted starches. Whenever the temperaturev of such starch mixture is raised, the granules of raw starch will begin: to swell. This indicates an absorption of water." Finally the granules will swell to such an'extent that they will rupture. The structure of the starch is therefore not completely, but only partially destroyed and a mass is formed consisting of the swollen starch particles which partially stick together.

Starch granules comprise two different starch modifications, namely, the amylose which is present in the interior of the starch granules, and the amylopectin which forms the outer layer and which forms the characteristic structure by which starches of different origin may be distinguished under the microscope.

from the amylopectin it would be found that the amylose would not be able to swell to form a paste with either hot or boiling water. The amylose is insoluble in water and also is insoluble in b'oiling water. The amylopectin is the substance from which the starch paste derives its viscous properties. v When raw starch is mixedwith water the raw starch separates out and precipitates and the granules of the raw starch do not change. If the temperature of the mixture is raised the granules of raw starch will commence to swell. The structure of the shell or outside layer, due to such swelling, is partly damaged, but the chemical structure of'the starch granule itself is not changed. The granules of starch will absorb water and grow larger and larger. The absorption of water by the granules is so large that the granules may be considered as watery aggregates of the original starch granules. The more water that is available, the more the granules will absorb and the'larger they will grow to such-an extent that the volume of the totality of the swollen granules is larger than the volume of the water. The above does not apply to the case where an exceedingly great excess of water is used. The swelling power of the starch granules will cause'a crowding whereby the soft swollen aggregates are pressed together and due to such pressing together they will stick together and will form a mass known as a paste which has a sticky characteristic.

The outside layers of the starch granules constituting the amylopectin are composed disregarding their chemical constitution of layers which tend to counteract the swelling and which still remain after the swelling. A boiled starch paste therefore is composed more or less, dependent upon the strength of the boiling process, of partly damaged swollenv portions of the amylopectin shells or layers which support or carry the amylose which has not the ability to swell. A boiled starch paste therefore is a starch which has been changed slightly physically but not changed chemically and the structure of the layers or shells isstill apparent therein and may with alkalies or acids, these chains are shortened and the more intensive the hydrolyzing process, the shorter the chainsbecome and therefore their dispersion in a vehicle the greater. The colloidal particles of the modified starch in a vehicle are therefore smaller. The formation of a soluble or modified starch by' chemical action as by the hydrolyzing process does not cause the structure of the layers of amylopectin to disappear entirely. Even when hydrolyzed to dextrine with the exception of the lower grades oi dextrine, the original physical structure of the starch granules may be recognized.

In the case of thin boiling, chemically treated, soluble or converted starches, the starch has been subjected to the hydrolyzing process with suitable che micals suchas acids, oxidizing agents, diastase, etc. which render the product more easily soluble in hot water. In this way the starch particles have become smaller and solutions are obtained therefrom with a lower viscosity. In such solutions the aqueous starch aggregates are smaller so that the solution has a higher dispersity. This .is also the case with alkali starches.

A cold swelling starch is also sharply distinguished from what is known as an attrition starch, such as is obtained by-grinding starch granules in a mill. In such. case the outer skin or layers of the starch granules are ruptured or otherwise mechanically broken. It is possible to separate an attrition starch into a soluble and an insoluble part by treating the same with water.

starch since a cold swelling starch gives a homogenized viscous paste when mixed with cold water. If an attrition starch formed a viscous paste, then it would obviously be impossible to separate the same. In order to make ,a paste from anattrition starch, it is. still necessary to boil or heat the same with water. An attrition starch therefore is not a cold swelling starch. An at-' trition starch does not gelatinize in the cold. An attrition starch absorbs aslightly larger amount of water than ordinary starch, but no gelatinization takes place in coldwater. cold swelling starch a homogenized paste is formed when mixed with cold water and not 'a product the granules of which swell in cold water to some extent without giving however a uniform mixture from which the swollen granules do not settle out on standing.

Cold swelling starches useful for the present purposes. and having the properties described may be manufactured in the following manner: raw starch is mixed with a small quantity of cold water; the amount being less than that ordinarily employed in boiling up starch. For example, with a starch ordinarily requiring about 8 In a.

giving a limited hydration. Usually the mixture is suddenly heated until far above the gelatinizing point. -A thick viscous mass is thereby produced which is simultaneously dried under mechanical pressure in thin layers. The dry product is subsequently ground to a granule size rather coarser than that of the original starch. The product so obtained when stirred with a large quantity of cold water, as for instance 10 to 15 parts water to 1 part cold swelling starch, will swell to a thick viscous mass. The properties of the jelly so obtained are widely different from those of the solutions 0! thin boiling, chemically treated, soluble,

attrition'or converted starches -or or a paste obtained by gelatinizing raw starch with warm or boiling water. When the cold swellingstarch is stirred with greater amountsof, water then it will form a good and fairly permanent dispersion.

After manufacture, the cold swelling starch should be so ground and sieved that the particles are substantially .larger than the granules of the original raw starch. The granules of raw-starch are so small that they may only be observed microscopically, which is not the case with the granules of cold swelling starch. The 'characteristic structure of ordinary granules of raw starch is not found in the new granules. Preferably the size of the particles of the cold swelling starch should be between a 10 mesh and 80 mesh sieve. By converting the starch into a cold swell.- ing starch the structure of the original starch granules has disappeared The particles are without any structure and have an irregular form.

The product obtained by allowing the cold swelling starch to swell in cold water has other properties than those of the other starches such as soluble, thin boiling, chemically treated, attrition or converted starches. This is equally the case with the solutions obtained from the different products owing to the fact that the particlesof the dried cold swelling starch are larger than 'the. original starch granules.

Therefore the swollen particles in the aqueous solution are also much larger than those obtained with' the starch products as used until now in the paper industry.

Also the results obtained with a cold swelling starch are better and more consistent. The fact that the results obtained with a cold swelling starch are so regular is especially appreciated by paper manufacturers. Ordinary starch is applied in three ways:

(11) Raw and unboiled,

(b) Swollen; that is, heated with water to a temperature of 70 C.,- and (c) Chemically treated by the user either'with oxidation agents or with alkali.

Each of the above three cases contain large sources of irregularities. There is an insufllcient utilization of the starches in each of the three cases mentioned. In the case of (b) above-there is an excess of heating for partof the starch and with respect to (0) above, there is an inferior opening for part of the starch granules. These things are responsible for the very irregular resuits obtained in the paper so' that the quantity of starch flxedin the paper formula can never .be considered as being definite and the working manager has always to estimate what additional quantities of starch are necessary, thereby runtirely from thou of boiled or heated starch.

These properties are brought forth by a cold swelling starch to a full 100% so that a formula with a cold swelling starch-will always give the parts, and if less water is .used in boiling the starch a rubbery plastic mass is obtained wherein the starch granules are insufficiently swollen due to lack of moisture and volume.

If a starch paste is dried and then ground, the product obtained will not thereafter swell with use into a paste since the product has become insoluble. As pointed out above, in manufacturing cold swelling starch for use in the present process the raw starch is mixed with very little water, for example only 10 2 parts and it is then suddenly heated to above the boiling point whereby a viscous mass is obtained that is dried at the same moment under mechanical presure by squeezing it out into thin layers which are then ground when dried. The product so obtained will swell with cold water into a paste or viscous mass and the jelly obtained from a cold swelling starch is not the same as that which is obtained by the boiling of starch into a paste as set forth above. In the process above described for forming cold swelling starch, the swelling of the starch granules is very heavily forced and at the same time due to the small quantity of water present the pressure of the granules upon each other is so great that the structure of the layers of amylopectin constituting the shells of the granules is entirely destroyed and the amylose and the amylopectin are apparently melted together into one uniform amorphous homogeneous mass which will have only amylopectin characteristics. When such mass is microscopically examined it will be found to have lost entirely the physical structure of the raw starch granules. Surprisingly the swelling power of the amylopectin re-' mains entirely available and gives to the composition entirely different characteristics and attributes from the composition obtained by boiling starch wherein the amylopectin orstarcn gran ule shells are only partly destroyed, a

A cold swelling starch due to the process above outlined for making the same differs materially from a modified or soluble starch in that in a cold swelling starch the change is not a chemical destruction or a 'hydrolization since the tributed throughout the paper; said cold swelling starch having been obtained by subjecting 1 part of raw starch mixed with 0.5 to 2 parts by weight of water to heat and pressure whereby said raw starch issimultaneously subjected to heat'above the gelatinization point and to pressure so as to burst the starch granules and forming cold swelling starch granules of substantially larger 'size than the granules of said raw Starch said cold swelling starch being present as an irreversible colloid little affected by moisture and temperature changes, said paper being resilient,

having high folding, Mullen and tearing strengths and being non-picking when printed.

2. A process of sizing paper comprising incorporating into the aqueous suspension of fibrousmaterial from which the paper is to be made, up to 5% by weight of a granular cold swelling starch which has been obtained by subjecting. 1 part of raw starch mixed with 0.5 to 2 parts by weight of water to heat and pressure whereby said raw starch is simultaneously subjected to sure so as to burst the starch granules and form'- ing said granular cold swelling starch with granules of substantially larger size than the granules of said raw starch, and then completing the manufacture of said paper whereby said paper is sized with said cold swelling starch, the said paper being resilient, having high folding, Mulion and tearing strengths and being non-picking parts by weight of water to heat and pressure 1 whereby said raw starch is simultaneously subjected to heat above the gelatinizationpoint and to pressure so as to burst the starch granules and forming said granular cold swelling starch with granules of substantially larger size than the granules of said raw starch. and then completing the manufacture of said paper whereby said paper is sized with said cold swelling starch, the said paper being resilient, having high folding, Mullen and tearing strengths and being nonpicking when printed and said paper having said cold swelling starch uniformly distributed throughout the paper.

4. In the manufacture of sized paper from beaten paper pulp the process which comprises adding to the pulp in the beater a minor proportion byweight of a granular cold swelling starch which has been obtained'by subjecting 1 part of raw starch mixed with 0.5 to 2 parts by weight of, water to heat and pressure whereby said raw starch is simultaneously subjected to heat above the gelatinization point and to pressure so as to burst the starch granules and forming said granular cold swelling starch with granules of substantially larger size than the granules of said raw starch, and thereafter converting the beaten pulp into paper, which is sized with said cold swelling starch, the said paper being resilient, having high folding, Mullen and tearing strengths and being non-picking when printed and said paper having said cold swelling starch uniformly distributed throughout the paper. i i

5. A process of sizing paper as set forth in claim 3 in which said granular cold swelling starch'is of such size that it will pass through a 10 to mesh screen.

6. A process of sizing paper comprising incorporating into the aqueous suspension of fibrous material from which the paper is to be made a,

minor proportionby'weightof a granular cold swelling starch which has been obtained by sub- -jecting 1 part of raw starch'mix'ed with 0.5 to 2 parts by weight of water to heat and pressure whereby said' raw starch is simultaneously subjected to heat above the gelatinization point and 10 heat above the gelatinization point and to presi starch, the said paper being resilient, having high folding; Mullen and tearing strengths and v of fibrous material is substantially neutral, then lowering the pH value to about 5 or less and then completing the manufacture 01 said paperwhere- ,by said paper is sized with said cold swelling being non-picking when printed and said paper having said cold swelling starch uniformly distributed throughout the paper.

7. A process as set forth in claim 6 in which.

alum is used to lower the pH value.

'JOHAN OL'I'MANS.

CERTIFICATE OF CORRECTION.

Patent No. 2,105,052.

'JOHAN- OLI'MANS January 11, v19 a It is hereby certified that error appealin the printed specification of the above numbered patent requiring correctionae follows: Page h, first column; line 7 for the word "without" read with; and that the said Letters Patent should be read'with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 19th day of July, A. D. 1953.

Seal.)

Henry Van Arsdale, Acting Commissioner of Patents starch, the said paper being resilient, having high folding; Mullen and tearing strengths and v of fibrous material is substantially neutral, then lowering the pH value to about 5 or less and then completing the manufacture 01 said paperwhere- ,by said paper is sized with said cold swelling being non-picking when printed and said paper having said cold swelling starch uniformly distributed throughout the paper.

7. A process as set forth in claim 6 in which.

alum is used to lower the pH value.

'JOHAN OL'I'MANS.

CERTIFICATE OF CORRECTION.

Patent No. 2,105,052.

'JOHAN- OLI'MANS January 11, v19 a It is hereby certified that error appealin the printed specification of the above numbered patent requiring correctionae follows: Page h, first column; line 7 for the word "without" read with; and that the said Letters Patent should be read'with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 19th day of July, A. D. 1953.

Seal.)

Henry Van Arsdale, Acting Commissioner of Patents 

